Laser survey instrument

ABSTRACT

A laser survey instrument, which comprises at least a main unit for emitting a laser beam and an object reflector for reflecting the laser beam from the main unit toward the main unit, whereby said main unit comprises an emitter for emitting the laser beam, a rotating unit for rotating and scanning the laser beam, a tilting mechanism for tilting the laser beam at an arbitrary angle at least in one direction with respect to a horizontal plane, a rotating angle detector interlocked with the rotating unit and for detecting irradiating direction of the laser beam, a reflection light detector for detecting reflection light from the object reflector, and an alignment display unit for detecting a deviation of direction with respect to the object reflector and a deviation of tilt angle based on a signal from the reflection light detector and for obtaining information on the deviation of direction or the tilt angle, the laser beam emitted from the main unit is irradiated to scan, the center of the object reflector is determined based on the laser beam reflected from the object reflector during scanning process, information on a deviation of direction of the main unit and a deviation of tilt angle is displayed, or direction and tilt angle of the main unit are corrected automatically based on the deviation of direction thus obtained or on the deviation of tilt angle thus obtained.

This application is a Divisional of application Ser. No. 08/598,322filed Feb. 8, 1996 U.S. Pat. No. 5,784,155.

BACKGROUND OF THE INVENTION

The present invention relates to a laser survey instrument, by which itis possible to provide a measurement reference plane by a laser beam,and in particular to provide, in addition to a horizontal referenceplane, an arbitrary tilt setting plane tilted at a given angle to thehorizontal reference plane.

Laser survey instruments are used for providing a horizontal referenceplane in wide range instead of optical level.

By such laser survey instruments, the horizontal reference line isformed by projecting a laser beam in a horizontal direction, or thehorizontal reference plane is formed by projecting the laser beam in ahorizontal direction via a rotating prism.

In architectural engineering work and civil engineering work,positioning and horizontal level setting are performed by utilizing thehorizontal reference plane. For example, a reference position isdetermined by the detection of the laser beam by a photodetector, andthis is used for setting-out of mounting position for windows or of ahorizontal line for ceiling in interior finishing work.

Also, as proposed by the present applicant in Japanese PatentPublication Laid-Open No. 6-26861, such a laser survey instrument is nowused not only for the setting of horizontal level but also in thesetting of tilt level, and it is widely used in construction work suchas the setting of water drainage inclination of a road or the setting ofa road surface gradient.

Description is now given on the laser survey instrument proposed inJapanese Patent Publication Laid-Open No. 6-26861, referring to FIGS. 28to 35.

At the center of a casing 5, a recess 6 in truncated conical shape isformed, and a support seat 7 is provided at the center of the recess 6.The support seat 7 comprises projections 9, which are protruded smoothlywith tertiary curved surface at 3 equally spaced positions on innerperiphery of a circular through-hole 8.

A laser projector 10 for emitting a laser beam is placed in thethrough-hole 8, and a head 11 of the laser projector 10 is engaged inand supported by the support seat 7. The head 11 has its lower portiondesigned in spherical shape, and this spherical portion 11a slidablycontacts the above three projections 9. The laser projector 10 issupported in such manner that it can be tilted in any direction withrespect to the vertical line.

A motor seat 14 is provided on the head 11, and a scanning motor 15 isarranged on the motor seat 14. A gear 16 is engaged with the outputshaft of a scanning motor 15. The gear 16 is engaged with a scanninggear 17, which is to be described later.

The axis of the laser projector 10 is aligned with the head 11 of thelaser projector 10, and a mirror holder 13 is rotatably arranged via abearing 12. The scanning gear 17 is engaged on the mirror holder 13. Asdescribed above, the scanning gear 17 is engaged with the gear 16 sothat the mirror holder 13 can be rotated around the vertical shaft bythe scanning motor 15. A pentagonal prism 18 is provided on the mirrorholder 13, and the laser beam emitted from the laser projector 10 isirradiated in a horizontal direction via a light projecting window 19.

At the middle portion of the laser projector 10, a sensor support shelf63 is arranged, on which fixed bubble tubes 20 and 21, serving astilting detectors for detecting the horizontality, are provided so thatthey are directed perpendicular to each other. The fixed bubble tubes 20and 21 are electric bubble tubes of capacitance detection type and eachof them issues an electrical signal corresponding to a tilt angle withrespect to the horizontal plane.

At the lower end of the laser projector 10, a base plate 64 ofapproximately in form of a right-angled triangle is fixed, and a strut70 is erected near the vertex of the rectangular portion of the baseplate 64, and a ball 67 is fixed on the upper end of the strut 70. AnL-shaped tilting plate 62 is arranged above the base plate 64, and aconical recess 99 is formed at the vertex on the rear surface of thetilting plate 62. The ball 67 is engaged with the recess 99, and theapical portion of the tilting plate 62 is supported on the strut 70 sothat the tilting plate 62 is pivotable on the ball 67. Further, a spring68 is provided between the tilting plate 62 and the base plate 64, andthe conical recess 99 is pressed against the ball 67, and the tiltingplate 62 is pushed clockwise in FIG. 28.

Arbitrary angle setting bubble tubes 65 and 66, serving as tiltingmovement detectors, are arranged on the tilting plate 62 along theL-shaped portion so that the arbitrary angle setting bubble tubes lie intwo directions perpendicular to each other.

A bearing plate 72 is positioned under the sensor support shelf 63 andis protruded from the laser projector 10. Tilting screws 52 and 53 arerotatably mounted at such positions on the base plate 64 as to form atriangle with the strut 70 at its vertex, and the upper ends of thetilting screws 52 and 53 are rotatably supported on the bearing plate72.

The lower end of the tilting screw 52 is protruded downward from thebase plate 64, and tilting gear 54 is engaged with the protruding end ofthe tilting screw 52. The tilting gear 54 is then engaged with a tiltinggear 56 to be described below. The lower end of the tilting screw 53 isprotruded downward from the base plate 64, and a tilting gear 55 isengaged with the protruding end of the tilting screw 53. The tiltinggear 55 is then engaged with a tilting gear 57 to be described below.

A tilting nut 48 is engaged on the tilting screw 52, and a nut pin 50having circular cross-section is protruded on the tilting nut 48. Atilting pin 60 having circular cross-section is protruded at suchposition on the end surface of the tilting plate 62 closer to thearbitrary angle setting bubble tube 65 as to be in parallel to thecenter line of the arbitrary angle setting bubble tube 65, and thetilting pin 60 is brought into contact with the nut pin 50. Further, twoparallel guide pins 71 are connected and they bridge between the baseplate 64 and the bearing plate 72, and the tilting pin 60 is slidablyheld by the two guide pins 71 in order to restrict rotation of thetilting plate 62 in a horizontal direction and to allow the tilting pin60 to rotate in a vertical direction and around the shaft of the tiltingpin 60.

A tilting nut 49 is engaged on the tilting screw 53, and a nut pin 51having circular cross-section is protruded at such position on thetilting nut 49. A tilting pin 61 having circular cross-section isprotruded at such position on the end surface of the tilting plate 62closer to the arbitrary angle setting bubble tube 66 as to be inparallel to the center line of the arbitrary angle setting bubble tube66, and the tilting pin 61 is brought into contact with the nut pin 51.

On the lower surface of the base plate 64, a post 73 is suspendedlymounted, and a tilt detecting piece 23, also serving as a motor base, isfixed via this post 73. On the upper surface of the tilt detecting piece23, tilting motors 58 and 59 are provided, and the tilting gear 56aforementioned is engaged on the output shaft of the tilting motor 58,and the tilting gear 57 is engaged on the output shaft of the tiltingmotor 59 so that the tilting gears 56, 57 are engaged with the tiltinggears 54 and 55 respectively.

On the lower surface of the tilt detecting piece 23, a ring-shapedreflection mirror is arranged. At positions face-to-face to the tiltdetecting piece 23, a given number (4 in the present embodiment) ofoptical sensors 24a, 24b, 24c and 24d are arranged, each of whichcomprises a set of light emitting elements and photodetector elements onthe same circumferential periphery around the shaft of the laserprojector when the casing 5 and the laser projector 10 are positionedperpendicularly to each other.

From the head 11 of the laser projector 10, tilting arms 25 and 26 areextended in horizontal directions and perpendicularly to each other. Thetilting arms 25 and 26 are passed through the conical surface of therecess 6 and are positioned inside the casing 5, and engaging pins 27and 28 are protruded at forward ends of the tilting arms 25 and 26. Theengaging pins 27 and 28 are designed in cylindrical shape, and the axesof the cylinders run perpendicularly to each other and are included in aplane, which passes through the center of the spherical portion 11a. Oneof the engaging pins 27 and 28, e.g. the engaging pin 27, is restrictedto move in horizontal direction so that it can be moved only in thevertical direction. Although not shown in the figure, the engaging pin27 is slidably engaged in a guide groove extending in the verticaldirection, or the engaging pin 27 is slidably pressed against the wallsurface extending in the vertical direction by a resilient means such asa spring.

Shelf plates 29 and 30 are provided on inner wall of the casing 5. Alevel adjusting motor 31 is arranged on the shelf plate 29, and a leveladjusting motor 32 is arranged on the shelf plate 30. A driving gear 33is engaged on the pivot shaft of the level adjusting motor 31, and thedriving gear 34 is engaged on the level adjusting motor 32. A screwshaft 35 running perpendicularly to the engaging pin 27 and bridgingover the ceiling of the casing 5 and the shelf plate 29 is rotatablyarranged. A driven gear 36 is engaged on the screw shaft 35, and thedriven gear 36 is also engaged with the driving gear 33. A slide nut 37is engaged with the screw shaft 35, and a pin 38 is protruded on theslide nut 37, and the pin 38 is slidably brought into contact with theengaging pin 27.

Similarly, a screw shaft 39 running perpendicularly to the engaging pin28 and bridging over the ceiling of the casing 5 and the shelf plate 30is rotatably arranged. A driven gear 40 is engaged with the screw shaft39, and the driven gear 40 is also engaged with the driving gear 34. Aslide nut 41 is engaged with the screw shaft 39, and a pin 42 isprotruded on the slide nut 41, and the pin 42 is slidably brought intocontact with the engaging pin 28.

A spring receptacle 43 is provided between the ceiling of the casing 5and the screw shaft 35 or the screw shaft 39, and a spring 44 is placedbetween the spring receptacle 43 and the laser projector 10 so that thelaser projector 10 is pushed clockwise around the support seat 7 in FIG.28.

In the figure, reference numeral 45 represents a battery box toaccommodate a battery for driving the laser survey instrument. The mainunit 4 of the laser survey instrument is mounted on a tripod (not shown)via leveling bolts 46 for leveling. Reference numeral 47 represents aglass window encircling the mirror holder 13.

FIG. 33 is a block diagram for a control unit of the above conventionaltype instrument.

Detection results of the fixed bubble tube 20 and the arbitrary anglesetting bubble tube 65 are inputted to an angle detection circuit 87 viaa switching circuit 85, and detection results of the fixed bubble tube21 and the arbitrary angle setting bubble tube 66 are inputted to anangle detection circuit 88 via a switching circuit 86. On the angledetection circuits 88 and 87, reference angles 92 and 91 are setrespectively. The reference angles 91 and 92 are usually 0°respectively.

When a signal from the fixed bubble tube 20 is inputted to the angledetection circuit 87 by the switching circuit 85, the angle detectioncircuit 87 detects a deviation from the reference angle 91, and thesignal of the angle detection circuit 87 is inputted to a motorcontroller 89. Then, the level adjusting motor 31 is driven andcontrolled by the motor controller 89.

When signals from the fixed bubble tube 20 and the arbitrary anglesetting bubble tube 65 are inputted to the angle detection circuit 87 bythe switching circuit 85, the angle detection circuit 87 issues a signalcorresponding to the deviation. This signal is inputted to a tiltdriving circuit 83, and the tilting motor 58 is driven and controlled bythe tilt driving circuit 83. When a signal from the arbitrary anglesetting bubble tube 65 is inputted to the angle detection circuit 87 bythe switching circuit 85, the angle detection circuit 87 detects thedeviation from the reference angle 91, and the signal of the angledetection circuit 87 is inputted to the motor controller 89. Then, thelevel adjusting motor 31 is driven and controlled by the motorcontroller 89.

The signal of the angle detection circuit 88 is inputted to a motorcontroller 90, and the level adjusting motor 32 is driven and controlledby the motor controller 90. A signal from the angle detection circuit 88and a signal from an arbitrary angle setter 82 are inputted to a tiltdriving circuit 84, and the tilting motor 59 is driven and controlled bythe tilt driving circuit 84.

The angular deviations of the angle detection circuits 87 and 88 areinputted to a discriminator 93. The discriminator 93 selects a higherangular deviation from the angular deviations of the angle detectioncircuits 87 and 88 and issues an output corresponding to the selectedangular deviation change to a display unit driver 94, which displays avalue corresponding to the deviation on a display unit 95.

A reference plane formed by laser beam can be set in horizontaldirection or at any angle. In the following, description will be givenon the leveling operation of the laser survey instrument to form thehorizontal reference plane.

When the main unit 4 is installed and no adjustment is made yet, theaxis of the laser projector 10 is generally not aligned with thevertical line, and the fixed bubble tubes 20 and 21 are not inhorizontal position. The switching circuits 85 and 86 operate in suchmanner that the signals from the fixed bubble tubes 20 and 21 areinputted to the angle detection circuits 87 and 88.

If it is assumed that the reference angles 91 and 92 are 0°respectively, angular deviation signals are outputted from the angledetection circuits 87 and 88. When the angular deviation signals areoutputted, the motor controllers 89 and 90 drive the level adjustingmotors 31 and 32 in a given direction so that the angular deviationsignals are turned to 0.

The operation relating to the level adjusting motors 31 and 32 is nowdescribed, taking an example in the case of the level adjusting motor31.

When the level adjusting motor 31 is driven, rotation of the leveladjusting motor 31 is transmitted to the screw shaft 35 via the drivinggear 33 and the driven gear 36, and the slide nut 37 is moved up or downby rotating the screw shaft 35. The upward or downward movement of theslide nut 37 is transmitted to the tilting arm 25 via the pin 38 and theengaging pin 27, and the laser projector 10 is tilted.

As described above, the movement of the engaging pin 27 is restricted inhorizontal direction and it is allowed to move only in verticaldirection. Thus, tilting direction of the laser projector 10 isrestricted and it is tilted around the axis of the engaging pin 28,which runs through the center of the spherical portion 11a. Next, whenthe level adjusting motor 32 is driven, the screw shaft 39 is rotated,and the engaging pin 28 is moved up or down via the pin 42.

Because the horizontal movement of the engaging pin 27 is restricted bya groove (not shown) and its vertical movement is restricted by the pin38 and the spring 44, the engaging pin 27 is allowed only to rotatearound the axis of the engaging pin 27, which runs through the center ofthe spherical portion 11a.

When the pin 42 is moved up or down, a change in vertical movement isgiven to the engaging pin 28 with sliding movement in axial directionbetween the pin 42 and the engaging pin 28, and the laser projector 10is tilted around the axis of the engaging pin 27. As described above,the cross-section of the engaging pin 27 is circular. Thus, the tiltingof the axis of the engaging pin 27 is not changed when the engaging pin27 is rotated. That is, tilting by the level adjusting motors 31 and 32give no influence on the other tilting axes, i.e. the tilting of theaxes of the engaging pins 27 and 28. Therefore, tilting adjustment ofone axis can be performed independently from the tilting adjustment ofthe other axis, and the operation of tilting adjustment and controlsequence relating to the operation of the tilting adjustment can beextensively simplified.

Because the laser projector 10 is pushed clockwise in FIG. 28 by thespring 44, the laser projector 10 accurately follows the movement of theslide nut 37.

In the tilting operation of the laser projector 10, the support of thelaser projector 10 is stable because the spherical portion 11a of thelaser projector 10 is supported at three points via the projections 9.Because it is the contact between the spherical portion 11a and theprojections 9 having smooth curved surfaces, the laser projector 10 issmoothly moved in any tilting direction, and the posture of the laserprojector 10 can be easily adjusted and controlled.

When the laser projector 10 is tilted and leveling operation proceeds,the detection values from the fixed bubble tubes 20 and 21 are broughtcloser to horizontal. Finally, angular deviations issued from the motorcontrollers 89 and 90 are turned to 0, and leveling operation iscompleted.

Detection range of the fixed bubble tubes 20 and 21 is narrow, andsaturation status occurs when it exceeds the predetermined range. Thus,tilting direction can be detected, but the value of the tilting anglecannot be detected. Therefore, the optical sensors 24a, 24b, 24c and 24dare provided so that the adjusting mechanism, comprising the leveladjusting motors 31 and 32, the driving gears 33 and 34, the drivengears 36 and 40, the screw shafts 35 and 39, the slide nuts 37 and 41,and the tilting arms 25 and 26, is not moved beyond the mechanicaladjusting range. Namely, when the limit of the mechanical adjustingrange is reached, the light emitted from one of the optical sensors 24a,24b, 24c and 24d is reflected by the reflection mirror arranged on thetilt detecting piece 23 and is detected by the optical sensor. As aresult, the reaching at the limit of the mechanical adjusting range isdetected, and the level adjusting motors 31 and 32 are stopped, or it isdisplayed on the display unit or a buzzer alarm is issued.

In such case, rough adjustment is made to fall in the adjusting range byutilizing the leveling bolts 46, and leveling operation will be startedagain.

When the leveling operation is completed, laser beam is emitted from thelaser projector 10. Further, the scanning motor 15 is driven to rotatethe laser projector 10 around the vertical axis, and laser beam isirradiated in horizontal direction through the pentagonal prism 18. Byrotating it further, a horizontal reference plane is formed by the laserbeam.

In the process of the leveling operation, some time is required from thestarting to the completion of leveling. During this period, the progressof the leveling operation is displayed for the operator to inform thatthe leveling operation is being performed adequately and to eliminatethe sense of uneasiness of the operator.

The magnitude of angular deviation issued from the angle detectioncircuits 87 and 88 is judged by the discriminator 93, and higher angulardeviation is selected. The change of the selected angular deviation isoutputted to the display unit driver 94, and the content of the displayis altered according to the change of the angular deviation. Then, it isdisplayed on the display unit 95.

The higher angular deviation is selected because more time is requiredfor angular adjustment of higher angular deviation. Instead of selectingmagnitude of angular deviation, the sum of the angular deviationsoutputted from the angle detection circuits 87 and 88 may be obtainedand the content of the display may be changed according to the sum ofthe angular deviations.

FIG. 34 is a diagram showing relationship between angular deviation andtime. Based on this relationship, a position to change the displaycontent is set in advance. When the angular deviation reaches the presetposition, the display is switched over, and the progress of the levelingoperation is notified to the operator.

Next, description is given on the case where the reference plane formedby the laser beam is set at an arbitrary angle after the horizontalreference plane is formed as described above.

The numerical values to tilt the reference plane by the arbitrary anglesetters 81 and 82 are inputted to the tilt driving circuits 83 and 84respectively.

It is determined whether or not the detection results of the fixedbubble tube 20 and the arbitrary angle setting bubble tube 65 areidentical with those of the fixed bubble tube 21 and the arbitrary anglesetting bubble tube 66, and these are made identical with each other. Inthis case, it is preferable that the fixed bubble tubes 20 and 21 are inhorizontal position, whereas these may not be in horizontal position andit will suffice if these are not in saturation status.

When the outputs from the fixed bubble tubes 20 and 21 and the arbitraryangle setting bubble tubes 65 and 66 are identical with each other, thearbitrary angle setting bubble tubes 65 and 66 are tilted at the anglesas set by the arbitrary angle setters 81 and 82, and the laser projector10 is tilted so that the arbitrary angle setting bubble tubes 65 and 66are turned to horizontal position. Then, the rotation axis of the laserprojector 10 for forming an arbitrary angle reference plane can beobtained. Thus, when the laser projector 10 is rotated to form areference plane, the laser beam reference plane is formed as desired.

Further, more concrete description will be given below. Because theangle setting operation for the arbitrary angle setting bubble tube 65is similar to the angle setting operation for the arbitrary anglesetting bubble tube 66, description will be given below only for thearbitrary angle setting bubble tube 65.

A switching signal is inputted to the switching circuit 85 from an inputunit or a control unit (not shown), and a signal from the fixed bubbletube 20 and a signal from the arbitrary angle setting bubble tube 65 areinputted to the angle detection circuit 87. In case deviation of anglesdetected by the fixed bubble tube 20 and the arbitrary angle settingbubble tube 65 is obtained in the angle detection circuit 87, and if adeviation is present, this deviation signal is inputted to the tiltdriving circuit 83.

The tilt driving circuit 83 drives the tilting motor 58. When thetilting motor 58 is driven, the tilting gear 56 is rotated, and therotation of the tilting gear 56 is transmitted to the tilting screw 52via the tilting gear 54, and the tilting nut 48 is moved up or down in agiven direction. When the nut pin 50 of the tilting nut 48 is engagedwith the tilting pin 60, the tilting plate 62 is tilted in such adirection that the deviation is turned to 0.

The tilting of the tilting plate 62 is detected by the arbitrary anglesetting bubble tube 65 and is further inputted to the angle detectioncircuit 87 via the switching circuit 85.

By the angle detection circuit 87, deviation of the detected angles ofthe fixed bubble tube 20 and the arbitrary angle setting bubble tube 65is sequentially calculated, and the detected angular deviation is fedback to the tilt driving circuit 83, and the tilting motor 58 is drivenuntil the detected angular deviation is turned to 0.

When the detected angular deviation is 0, the axis of the laserprojector 10 runs perpendicularly to the plane detected by the arbitraryangle setting bubble tubes 65 and 66.

Next, the preset angle is inputted to the tilt driving circuit 83 by thearbitrary angle setter 81, and the tilting reference plane settingoperation is started.

In the tilt driving circuit 83, the tilting motor 58 is driven so thatthe angle corresponding to the preset angle inputted by the arbitraryangle setter 81 is reached, and the tilting plate 62 is tilted in adirection reverse to the tilting reference plane to be obtained.

Here, for example, a pulse motor is used as the tilting motor 58, andthe tilting angle of the tilting plate 62 and the number of pulses ofthe pulse motor required for the tilting are stored in the tilt drivingcircuit 83 in advance. Then, the number of pulses corresponding to theangle set by the arbitrary angle setter 81 is outputted to drive thetilting motor 58.

The tilting screw 52 is rotated by the tilting motor 58, and the tiltingnut 48 is moved in a given direction, e.g. in downward direction.

The movement of the tilting nut 48 is transmitted to the tilting plate62 via the nut pin 50 and the tilting pin 60 as described above, and thetilting plate 62 is tilted counterclockwise in FIG. 28 around the ball67.

As already described, the tilting pin 60 is guided by the guide pin 71and is tilted only in vertical direction. Accordingly, the tilting ofthe tilting pin 60 gives no influence on the tilting of the arbitraryangle setting bubble tube 66.

When the tilting plate 62 is tilted, the output value from the angledetection circuit 87 is changed, and the comparison result calculated bythe tilt driving circuit 83 decreases.

When the comparison result is turned to 0, the driving of the tiltingmotor 58 is stopped, and the tilting setting operation of the tiltingplate 62 is completed. The signal of this completion is also inputted tothe switching circuit 85, and the circuit is switched over in suchmanner that only the signal from the arbitrary angle setting bubble tube65 is inputted to the reference angle 91.

The tilting operation relating to the arbitrary angle setting bubbletube 66 is also performed in similar manner. Because the tilting pin 60is guided by the guide pin 71 as described above, the tilting operationof the arbitrary angle setting bubble tube 66 gives no influence on thearbitrary angle setting bubble tube 65. Therefore, the tiltingoperations in two directions of the tilting plate 62 can beindependently controlled, and control sequence relating to thetwo-direction tilting operation of the tilting plate 62 is simple.

When the tilting setting operation of the tilting plate 62 is completed,tilting operation of the laser projector 10 is started based on thedetection results of the arbitrary angle setting bubble tube 65 in orderto set the tilting reference plane. The setting operation of the tiltingof the laser projector 10 is performed in such manner that the detectionresults of the arbitrary angle setting bubble tube 65 are in ahorizontal direction. Because this operation is similar to the casewhere leveling operation is performed based on the fixed bubble tubes 20and 21, detailed description is not given here.

FIG. 32 represents the status where the setting operation of the tiltingreference plane has been completed. When the setting operation of thetilting reference plane is completed, the tilting plate 62 is inhorizontal position.

The concurrent operation of the fixed bubble tube 20 and the arbitraryangle setting bubble tube 65 is carried out to guarantee the accuracy ofthe tilting operation of the tilting plate 62. This may be performedeach time the tilting operation is carried out or after it has beenrepeated by the predetermined times.

FIG. 35 represents an example of a controller 96 incorporated with thearbitrary angle setters 81 and 82. The tilting of the tilting plate 62is supported by the tilting of two axes (X and Y), and the presetnumerical values are displayed on the display units 97 and 98.

In the above, it is described that adjustment has been already completedas to in which direction the reference plane formed by laser beam shouldbe tilted. In fact, accurate setting must be made first in a desireddirection (horizontal direction), in which the main unit 4 of the lasersurvey instrument should be tilted.

In the past, to perform the setting operation to set the main unit in adirection to be tilted, a collimator 75 arranged on the upper surface ofthe main unit 4 as shown in FIG. 28 has been used. Tilting direction ofthe tilt setting mechanism in the main unit is set in parallel tolongitudinal direction of the bubble tube, which sets and detects thetilting, and mechanical arrangement is made in such manner thatcollimating direction of the collimator 75 is also in parallel to thetilt setting mechanism. The direction of the main unit is also alignedwith the tilt setting mechanism. The operation to set the collimator 75in a direction to be tilted is to rotate or move the main unit and toturn the tilting direction of the tilt setting mechanism in the mainunit and the bubble tube toward the predetermined direction. In themeantime, the main unit is usually mounted on a tripod, and descriptionwill be given now on the operation on the tripod.

A target (not shown) is installed in advance in a direction, in whichthe tilting should be set, and by directing the main unit of the lasersurvey instrument in a direction accurately facing to the target usingthe collimator 75, main unit 4 can be set in the direction, in which itis to be tilted.

The screws (not shown) fixing the main unit 4 are loosened, and the mainunit 4 is rotated. The target is collimated from the collimator 75, andthe direction of the main unit 4 is accurately set toward the target.

As it is evident from the above description, the horizontal line is usedas reference in the setting of an internal tilt angle (an angle ofelevation) in a series of setting operations for the laser surveyinstrument, and it is performed according to tilting informationelectrically detected by a tilt detector such as bubble tube. Thus,there will be no man-made error by the surveyor. As a result, tilt anglecan be set at high accuracy.

On the other hand, in the operation to set the main unit 4 in adirection to be tilted, the collimator 75 is used, and it is up topersonal judgment of the surveyor to decide whether it is aligned ornot. Further, the collimator 75 requires no high technical skill tocollimate, and unlike a collimating telescope, collimating accuracy isnot high. For this reason, the setting by means of the collimator 75does not give high accuracy in the setting of the direction because oflow accuracy of the collimator itself and of the man-made error.

In conventional type civil engineering work, which does not necessarilyrequire high accuracy, there has been no special problem in thedirection setting using the collimator 75, whereas, in the highlymechanized civil engineering work in recent years, the problem ofaccuracy arises.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a laser surveyinstrument, by which it is possible to perform the setting of the lasersurvey instrument at high accuracy in case angle of elevation is to beset for the laser survey instrument, and further, it is possible toperform automatically more accurate setting of tilt angle by eliminatingman-made error.

To attain the above object, the laser survey instrument according to thepresent invention comprises at least a main unit for emitting a laserbeam and an object reflector for reflecting the laser beam from the mainunit toward the main unit, wherein the main unit comprises an emitterfor emitting the laser beam, a rotating unit for rotating and scanningthe laser beam, a tilting mechanism for tilting the laser beam at anarbitrary angle at least in one direction with respect to a horizontalplane, a rotating angle detector interlocked with the rotating unit andfor detecting irradiating direction of the laser beam, a reflectionlight detector for detecting reflection light from the object reflector,and an alignment display unit for detecting a deviation of directionwith respect to the object reflector based on a signal from thereflection light detector and for obtaining information on the deviationof direction, whereby the reflection light detector detects the positionof the center of gravity of the reflected photodetection signal and toidentify the center of the object reflector, or the emitter modulatesthe laser beam and the reflection light detector is provided with afilter for detecting the modulated laser beam , or in case the laserbeam entering the object reflector is circularly polarized light, theobject reflector comprises a polarized light maintaining reflectingsurface for reflecting the light while maintaining circularly polarizedlight of the incident laser beam and a polarized light convertedreflecting surface for reflecting the light in circularly polarizedlight different from the circularly polarized light of the incidentlaser beam, the emitter of the main unit emits laser beam of circularlypolarized light, and the reflection light detector separates the laserbeam of the emitted circularly polarized light from the laser beam ofcircularly polarized light different from the emitted circularlypolarized light and detects the boundary between two reflecting surfacesof the object reflector, or the main unit is provided on a main unitrotator, and the main unit rotator can rotate the main unit around avertical axis, or the main unit is provided on a main unit rotator, andthe main unit rotator can rotate the main unit around a vertical axis,or the alignment display unit is provided with a display unit fordisplaying a calculated deviation of direction of the main unit withrespect to the object reflector, or the alignment display unit isprovided with a rotation controller for controlling the main unitrotator in such manner that the main unit is accurately directed towardthe object reflector based on a calculated deviation of direction of themain unit with respect to the object reflector, or the rotating angledetector is an encoder and the encoder has at least one index, or thereis provided an optical means for emitting the laser beam in twodirections, i.e. upward and downward directions, from the emitter, or awidth of a reflection layer formed on the object reflector is graduallychanged in vertical direction, or the width of the reflection layerformed on the object reflector has an extreme value at a given positionin vertical direction, or the object reflectorhas reflection layersdivided into two portions, and widths of the two reflection layers arechanged as positions are changed in vertical direction, or the objectreflector has a plurality of belt-like reflection layers, and aplurality of pulse-like laser beams are reflected in case the objectreflector is irradiated and scanned, or in case the laser beam enteringthe object reflector is circularly polarized light, the object reflectorhas a polarized light maintaining reflecting surface for reflecting thelight while maintaining the circularly polarized light of the incidentlaser beam and a polarized light converted reflecting surface forreflecting the light in circularly polarized light different from thecircularly polarized light of the incident laser beam, and widths of thetwo reflecting surfaces are changed as the positions are changed invertical direction, or irradiating and scanning position of the objectreflector is moved in vertical direction, and the reflection lightdetector detects the center or a target in vertical direction based onthe change in width of the laser beam reflected from the objectreflector, or a tilt angle from the horizontal plane is displayed on adisplay unit based on output from the tilting mechanism corresponding tothe tilting of the tilting mechanism in case the target center of theobject reflector is detected, or the object reflector has reflectionlayers divided into upper and lower portions, and the target center invertical direction is detected by determining the position of the centerof gravity of the laser beam reflected from the object reflector asobtained in case the laser beam is irradiated and scanned with respectto the object reflector in vertical direction, or there is provided amanual setting mechanism for manually performing tilt setting of thetilting mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a mechanical portion of anembodiment of the present invention;

FIG. 2 is a block diagram of an optical system and a control system ofthe above embodiment;

FIG. 3A and FIG. 3B each represents an example of an object reflector;

FIG. 4A and FIG. 4B each represents an example of another objectreflector;

FIGS. 5A, 5B, 5C, 5D, 5E and 5F are drawings for showing operation ofthe above embodiment;

FIG. 6 is a block diagram of an optical system and a control system of asecond embodiment of the present invention;

FIG. 7 is a circuit diagram of an example of a reflection lightdetection circuit of the second embodiment;

FIG. 8 is a perspective view of an object reflector used in the secondembodiment;

FIG. 9 represents diagrams for explaining operation of the reflectionlight detection circuit;

FIG. 10A and FIG. 10B each represents relationship of outputs from theobject reflector, the laser beam and the reflection light detectioncircuit;

FIG. 11 is a block diagram of an emitter of a third embodiment of thepresent invention;

FIG. 12 is a front view of an angle display disk used in the presentinvention;

FIG. 13 is a cross-sectional view of a laser survey instrument equippedwith a manual adjusting mechanism capable to manually adjust thedirection of a main unit;

FIG. 14 is a plan view of an essential portion of the above manualadjusting mechanism;

FIG. 15 is a block diagram of a laser survey instrument equipped with amechanism capable to manually adjust tilt angle of the laser beam to beirradiated;

FIGS. 16A, 16B and 16C are drawings for explaining operation in casetilting of the laser beam to be irradiated is determined by utilizingthe object reflector;

FIGS. 17A, 17B and 17C are drawings for explaining operation in casetilting of the laser beam to be irradiated is determined by utilizingthe object reflector;

FIG. 18 is a flow chart showing operation in case tilting of the laserbeam to be irradiated is determined by utilizing the object reflector;

FIG. 19 is a flow chart showing operation in case tilting of the laserbeam to be irradiated is determined by utilizing the object reflector;

FIG. 20A and FIG. 20B each represents an example of the objectreflector;

FIG. 21A and FIG. 21B each represents an example of another objectreflector;

FIG. 22A and FIG. 22B each represents an example of a still anotherobject reflector;

FIG. 23 represents an example of a yet still another object reflector;

FIG. 24 represents an improved example of the object reflector;

FIG. 25A and FIG. 25B each represents relationship of outputs from theobject reflector, the laser beam, and the reflection detection circuit;

FIG. 26 is a block diagram of an optical system and a control system ofa fifth embodiment of the present invention;

FIG. 27A and FIG. 27B each represents an object reflector used in thefifth embodiment;

FIG. 28 is a cross-sectional view of a conventional example;

FIG. 29 is an arrow diagram along the line A--A in FIG. 28;

FIG. 30 is an arrow diagram along the line B--B in FIG. 28;

FIG. 31 is an arrow diagram along the line C--C in FIG. 28;

FIG. 32 is a drawing for explaining operation of the conventionalexample;

FIG. 33 is a block diagram of a control system of the conventionalexample;

FIG. 34 is a diagram showing leveling status; and

FIG. 35 is an illustration of an example of a controller.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, description will be given on an embodiment of thepresent invention referring to the drawings.

In the present invention, an object (an object reflector 168) is placedin a direction to be tilted, and a main unit 4 itself recognizes thetilting, and direction of tilting of the main unit 4, or substantiallytilting of a tilt setting mechanism, with respect to the objectreflector 168 is corrected. In FIGS. 1 and 2, the same component as inFIGS. 28 to 35 is referred by the same symbol, and detailed descriptionis not given here.

First, the mechanical portion will be described referring to FIG. 1. Amain unit rotator 151 is mounted under a battery box 45. Description isnow given on the main unit rotator 151.

A rotation base 152 is fixed on the lower surface of the battery box 45,and a rotating shaft 153 is protruded downward from the rotation base152. A rotation frame 154 is fixed on the rotation base 152, and therotation frame 154 is rotatably mounted on a hollow fixed frame 156 viaa bearing 155. The rotating shaft 153 passes through the rotation frame154. A rotating gear 157 is fixed on the rotating shaft 153, and a slipring 158 is engaged on the forward end of the rotating shaft 153. Acontact 159 contacts the slip ring 158, and driving electric power andcontrol signals are supplied from the main unit via the slip ring 158and the contact 159. A rotating motor 160 is arranged on the bottomsurface of the fixed frame 156, and an output gear 161 engaged with anoutput shaft of the rotating motor 160 is engaged with the rotating gear157. An encoder 150 is arranged between the rotation frame 154 and thefixed frame 156, and an angle between the rotation frame 154 and thefixed frame 156, i.e. relative rotating angle of the main unit 4 withrespect to the fixed frame 156, is detected by the encoder 150, and therotating angle thus detected is inputted to a rotation controller 169.The rotating motor 160 is driven by the rotation controller 169, androtation is controlled.

On the lower surface of the fixed frame 156, bolt holes (not shown) formounting on a tripod are formed, and the fixed frame 156 is mounted onthe tripod (not shown) via the bolt holes. Reference numeral 46represents a bolt for leveling adjustment.

Next, description will be given on optical and control systems inconnection with FIG. 2.

The main unit 4 comprises an emitter 162, a rotating unit 163, areflection light detector 164, a scanning controller 165, a lightemitting element driving unit 166, and an alignment display unit 167.

First, the emitter 162 is described.

On the optical axis of a laser diode 101, a collimator lens 102 and aperforated mirror 103 are arranged in this order as seen from the laserdiode 101. Laser beam emitted from the laser diode 101 is turned toparallel beams through the collimator lens 102, and the beams aredirected toward the rotating unit 163 through the perforated mirror 103.Light beam is emitted from the laser diode 101 by the light emittingelement driving unit 166. The light is modulated by the light emittingelement driving unit 166, and the laser beam emitted from the laserdiode 101 can be discriminated from the other external light.

The rotating unit 163 directs the laser beam emitted from the emitter162 in horizontal direction for scanning. A pentagonal prism 18 fordeflecting optical axis of the laser beam from the emitter 162 by anangle of 90° is supported in such manner that it can be rotated aroundthe optical axis of the emitter 162. Further, it is rotated by thescanning motor 15 via a gear 16 and a scanning gear 17. An encoder 105is provided with respect to the rotating shaft of the pentagonal prism18.

The encoder 105 comprises a rotor 109 and a detector 107, and it is anincremental encoder equipped with an index 108 for showing a referenceposition (FIG. 5). By counting an output from the reference positiongiven by the index 108, an angle from the reference position can bedetected. The index 108 for showing the reference position is arrangedin such manner that it is detected by the detector 107 when irradiatingdirection of the rotating laser beam is aligned with tilting directionof the tilt setting mechanism, i.e. when the laser beam is in parallelto the arbitrary angle setting bubble tube 65.

The object reflector 168 reflects the laser beam toward the rotatingunit 163 when the laser beam emitted from the rotating unit 163 isirradiated. The object reflector 168 is shown, for example, in FIGS. 3Aand 4A. The object reflector shown in FIG. 3A has a reflection layer 122on a substrate 121 and reflects the light from the rotating unit 163 sothat the light enters the rotating unit 163 again. The reflection layer122 is a retroreflective surface, comprising beads, very small prisms,etc. In the object reflector shown in FIG. 4A, reflection layers 122 arearranged on two lateral portions of the substrate 121. Thus, there aretwo reflection layers to easily discriminate between reflection from theobject reflector 168 and reflection from unnecessary reflecting object.

When the object reflector 168 shown in FIG. 3A is scanned by the laserbeam, the laser beam reflected from the object reflector 168 is turnedto pulse-like beam having the same width as that of the object reflector168 as shown in FIG. 3B. When the object reflector 168 shown in FIG. 4Ais scanned by the laser beam, the laser beam reflected from the objectreflector 168 shown in FIG. 4B exhibits two-pulse form varied from theform of the beam of FIG. 3B, lacking the intermediate portion.

The laser beam reflected from the object reflector 168 enters thepentagonal prism 18. Upon entering the pentagonal prism 18, thereflection laser beam is deflected toward the perforated mirror 103, andthe perforated mirror 103 directs the reflection laser beam toward thereflection light detector 164.

Next, description will be given on the reflection light detector 164.

On the optical axis of the reflection light from the perforated mirror103, a condenser lens 110 and a first photodetector 114 comprising aphotodiode and the like are sequentially arranged in this order as seenfrom the perforated mirror 103 so that the first photodetector 114receives the reflection laser beam from the object reflector 168, andoutput from the first photodetector 114 is inputted to a reflectionlight detection circuit 116. The reflection light detection circuit 116is equipped with an electric filter (not shown) for detectingphotodetection signals of the laser beam. Of the photodetection signalsfrom the first photodetector 114, the modulated laserbeam is extractedand detected from the other external light. Further, the signal isprocessed, e.g. amplified, and is outputted to the alignment displayunit 167.

The alignment display unit 167 comprises a position discriminator 117and a display unit 118. A signal showing photodetection status of thefirst photodetector 114 from the reflection light detection circuit 116is inputted to the position discriminator 117, and an angle signal fromthe encoder 105 for detecting rotating position of the pentagonal prism18 on the rotating unit 163 is inputted. The angle signal from theencoder 105 is an angle signal of the encoder 105 correspondingphotodetection status when the reflection laser beam from the objectreflector 168 is received. Therefore, by obtaining the signal of theencoder 105 at leading and trailing edges of the signal (FIG. 3B)obtained by receiving the reflection laser beam from the objectreflector 168 shown in FIG. 3, and an angle signal from the referenceposition, it is possible to easily detect the position of the center ofgravity of the object reflector 168, and the center of the objectreflector 168. Also, for the object reflector 168 shown in FIG. 4, byobtaining the signal of the encoder 105 at leading and trailing edges ofthe signal (FIG. 4B) obtained by receiving the reflection laser beam,and an angle signal from the reference position, it is possible todetect position of the center of gravity of the object reflector 168,i.e. the center of the object reflector 168.

The position discriminator 117 calculates the position of the center ofgravity of the photodetection signal, i.e. the center of the objectreflector 168, from the photodetection signal of the reflection lightdetection circuit 116 and the angle signal of the encoder 105, and theresult of the calculation is inputted to the display unit 118 and therotation controller 169. If the direction of the-main unit 4 isdeviated, the display unit 118 indicates the corrected direction of themain unit 4 by arrows 118a or 118c. Further, in case the main unit 4 isaccurately positioned face-to-face to the object reflector 168, it isindicated by a display indicator 118b at the center.

In the following, description will be given on operation referring toFIG. 5.

After horizontal leveling operation of the main unit 4 has beencompleted (FIG. 5A), the rotating unit 163 is rotated by the scanningmotor 15, and the laser beam emitted from the emitter 162 is scanned onthe horizontal plane. Rotating position of the rotating unit 163 isdetected by the encoder 105. On a rotating plate of the encoder 105,which is integrally rotated with the rotating unit 163, a main scale forissuing angle pulses and an index 108 for showing reference position aremarked. A detector 107 on the encoder 105 on the fixed side of the mainunit 4 issues angle pulses by the main scale and a reference positionpulse by the index 108. Mechanical relation between the encoder 105 andthe main unit is set in such manner that the laser beam is directedtoward the direct front of the main unit 4, or substantially towardtilting direction of the tilt setting mechanism. When the main unit 4 isinstalled, the main unit 4 is not accurately facing toward the objectreflector 168 generally. As shown in FIG. 5B, it is assumed here thatthe main unit 4 is deviated by an angle of W counterclockwise in thefigure.

When the laser beam scans the plane and the rotating unit 163 isrotated, the detector 107 detects the index 108. Then, the referenceposition is confirmed, and a rotating angle of the rotating unit 163 isdetected by the encoder 105 from the detected position (FIG. 5C).Further, the rotating unit 163 is rotated, and when the laser beampasses through the object reflector 168, the reflection laser beam fromthe object reflector 168 enters the reflection light detector 164 viathe rotating unit 163 and the perforated mirror 103, and the firstphotodetector 114 issues photodetection signal. The reflection lightdetection circuit 116 extracts the photodetection signal containing onlythe laser beam and outputs it to the position discriminator 117. At theposition discriminator 117, the center position of the object reflector168 is calculated, and an angle signal from the encoder 105 relating tothe center position is read. This angle is nothing but a deviation ofthe direction of the main unit 4 with respect to the object reflector168, i.e. the angle ω (FIG. 5D). The direction or the amount relating toω is indicated by the arrow 118a, the display indicator 118b, or thearrow 118c. The angle signal ω is inputted to the rotation controller169. The rotation controller 169 issues a driving signal to the rotatingmotor 160 to drive it, and the rotating motor 160 rotates the main unit4 toward the direction to be corrected via the output gear 161 and therotating gear 157. The rotating angle of the main unit 4 is detected bythe encoder 150, and the rotating motor 160 is stopped when the angledetected by the encoder 150 is turned to ω (FIG. 5E).

When the main unit 4 is accurately faced toward the object reflector168, an angle of elevation ω is set, and the scanning motor 15 is drivento irradiate the laser beam for scanning. Then, a reference plane tiltedby the angle of elevation ω with respect to the target is formed (FIG.5F).

The detection of the direction of the main unit 4 is not limited to theencoder 150.

Description is now given on a second embodiment referring to FIG. 6. Inthis second embodiment, the object reflector 168 has a reflection layer122 formed on a substrate 121 as shown in FIG. 8. On the left half inthe figure, a λ/4 birefringence member 123 is attached. Thus, forexample, the exposed portion of the reflection layer 122 serves as apolarized light maintaining reflecting unit, which reflects the lightwhile maintaining direction of polarization of the incident light beam,and the λ/4 birefringence member 123 serves as a polarized lightconverted reflecting unit, which reflects the light while convertingdirection of polarization from that of the incident light beam, thusgiving different directions of polarization.

The reflection layer 122 comprises a retroreflective material, i.e. ithas a plurality of very small corner cubes, or spherical objectreflectors. The λ/4 birefringence member 123 fulfills such function thatthe polarized light reflection light beam causes phase difference of λ/4with respect to the incident light beam.

Next, description will be given on the main unit 4 in the secondembodiment.

On the optical axis of a laser diode 101, which emits linearly polarizedlaser beam, a collimator lens 102, a first λ/4 birefringence member 104and a perforated mirror 103 are sequentially arranged in this order asseen from the laser diode 101. The linearly polarized laser beam emittedfrom the laser diode 101 is turned to parallel beams by the collimatorlens 102, and the beams are further converted to circularly polarizedlight by the first λ/4 birefringence member 104. The circularlypolarized laser beam is directed toward the rotating unit 163 throughthe perforated mirror 103. The rotating unit 163 irradiates the laserbeam coming from the emitter 162 in horizontal direction for scanning.

The polarized reflection laser beam from the object reflector 168 entersthe rotating unit 163. Upon entering the pentagonal prism 18, thepolarized light reflection laser beam is deflected toward the perforatedmirror 103, and the polarized reflection laser beam is reflected on theperforated mirror 103 and directed toward the reflection light detector164.

Next, description will be given on the reflection light detector 164.

On the optical axis of reflection light of the perforated mirror 103, acondenser lens 110, a second λ/4 birefringence member 111, a pinhole112, a polarized light beam splitter 113, and a first photodetector 114comprising a photodiode and the like are sequentially arranged in thisorder as seen from the perforated mirror 103, and a second photodetector115 comprising a photodiode and the like is arranged on reflectionoptical axis of the polarized light beam splitter 113. Outputs from thefirst photodetector 114 and the second photodetector 115 are inputted tothe reflection light detection circuit 116.

The polarized light beam splitter 113 splits the polarized reflectionlaser beam entering the reflection light detector 164 and allows thesplit beams to enter the first photodetector 114 and the secondphotodetector 115. The second λ/4 birefringence member 111 and thepolarized light beam splitter 113 are arranged in such manner that thelaser beam emitted from the emitter 162 transmits the λ/4 birefringencemember 123 twice and the polarized reflection laser beam returning tothe main unit enters the first photodetector 114, and that the laserbeam from the reflection layer 122 having a different direction ofpolarization from that of the above laser beam enters the secondphotodetector 115.

Description is now given on an example of the reflection light detectioncircuit 116 which detects the polarized reflection laser beam referringto FIG. 7.

Outputs of the first photodetector 114 and the second photodetector 115are inputted to a differential amplifier 132 via amplifiers 131 and 135,and output of the differential amplifier 132 is inputted to adifferential amplifier 134 via a synchronous detector 133. Outputs ofthe first photodetector 114 and the second photodetector 115 areinputted to a summing amplifier 136 via the amplifiers 131 and 135.Output of the summing amplifier 136 is inputted to a differentialamplifier 139 via a synchronous detector 138. Outputs of thedifferential amplifiers 139 and 134 are inputted to a scanningcontroller 165, a light emitting element driving unit 166, and analignment display unit 167. The light emitting element driving unit 166performs pulse modulation of the polarized laserbeam emitted from thelaser diode 101 based on a clock signal from the reflection lightdetection circuit 116.

The polarized laser beam emitted from the laser diode 101 driven by thelight emitting element driving unit 166 is modulated based on a clocksignal from an oscillator circuit 140. The linearly polarized laser beamemitted from the laser diode 101 is turned to parallel beams by thecollimator lens 102, and the beams are turned to circularly polarizedlaser beam after passing through the first λ/4 birefringence member 104.The circularly polarized laser beam passes through the perforated mirror103, is deflected in horizontal direction by the pentagonal prism 18,and is irradiated.

The pentagonal prism 18 is rotated by the scanning motor 15 via the gear16 and the scanning gear 17. The pentagonal prism 18 is rotatedinitially over the total circumferential direction, and the polarizedlaser beam irradiated from the pentagonal prism 18 scans in totalcircumferential direction.

By scanning in total circumferential direction, the polarized laser beampasses through the object reflector 168. When passing through it, thepolarized laser beam is reflected by the object reflector 168, and thepolarized reflection laser beam enters the pentagonal prism 18.

As described above, one-half of the object reflector 168 is simply thereflection layer 122, and the λ/4 birefringence member 123 is attachedon the other half. Therefore, the polarized reflection laser beamreflected by the exposed portion of the reflection layer 122 iscircularly polarized light, maintaining direction of polarization of theincident polarized laser beam. The polarized reflection laser beam,which passes through the λ/4 birefringence member 123 and is reflectedby the reflection layer 122, further passes through the λ/4birefringence member 123, is turned to circularly polarized laser beam,which is deviated by λ/2 in phase with respect to the direction ofpolarization of the incident polarized laser beam. Thus, the directionsof polarization are different depending upon the reflection surfaces.

The polarized reflection laser beam reflected by the object reflector168 is deflected by an angle of 90°38 by the pentagonal prism 18 andenters the perforated mirror 103, which reflects the reflection laserbeam toward the condenser lens 110. The condenser lens 110 directs thereflection laser beam as convergent light toward the second λ/4birefringence member 111. Returning as circularly polarized light, thereflection laser beam is converted to linearly polarized light by thesecond λ/4 birefringence member 111 and enters the pin hole 112. Asdescribed above, the reflection laser beam reflected by the exposedportion of the reflection layer 122 is different from the reflectionlaser beam reflected by the λ/4 birefringence member 123 in that thephase is deviated by λ/2, and the plane of polarization is different anddeviated by 90° between the two reflection laser beams converted tolinearly polarized light by the second λ/4 birefringence member 111.

The pinhole 112 fulfills such function that it does not allow thereflection laser beam, not accurately facing to and having optical axisdeviated from that of the polarized laser beam emitted from the mainunit 4, to enter the first photodetector 114 and the secondphotodetector 115, and the reflection laser beam enters the polarizedbeam splitter 113 after passing through the pinhole 112.

The polarized light beam splitter 133 allows the laser beam to pass,which has the same direction of polarization as that of the polarizedlaser beam emitted from the emitter 162, and it reflects the laser beamhaving a different direction of polarization deviated by 90° from thatof the polarized laser beam emitted from the emitter 162. Thus, uponpassing through the polarized light beam splitter 113, the reflectionlaser beam is split into polarized light components runningperpendicularly to each other by the polarized light beam splitter 113,and the first photodetector 114 and the second photodetector 115 receivethe split reflection laser beams respectively.

In the light receiving status of the first photodetector 114 and thesecond photodetector 115, when the polarized reflection laser beam afterpassing through the λ/4 birefringence member twice outside the main unit4, i.e. the polarized reflection laser beam reflected by the λ/4birefringence member 123 of the object reflector 168, enters thereflection light detector 164, and the light quantity entering the firstphotodetector 114 is higher than the light quantity entering the secondphotodetector 115 because of the relationship between the second λ/4birefringence member 111 and the polarized light beam splitter 113.Also, when the polarized reflection laserbeam not passing through theλ/4 birefringence member, i.e. the polarized reflection laser beamreflected by the exposed portion of the reflection layer 122 of theobject reflector 168, the light quantity entering the secondphotodetector 115 is higher than the light quantity entering the firstphotodetector 114.

By finding out the difference between the incident light quantity of thepolarized reflection laser beam to the first photodetector 114 and theincident light quantity to the second photodetector 115, it is possibleto determine whether the incident polarized reflection laser beam hasbeen reflected by the exposed portion of the reflection layer 122 of theobject reflector 168 or it has been reflected by the λ/4 birefringencemember 123. That is, it is possible to detect the boundary between theexposed portion of the reflection layer 122 and the λ/4 birefringencemember 123, i.e. the center of the object reflector 168.

More detailed description will be given below.

In case of the reflection laser beam after passing through the λ/4birefringence member 123 twice, the light quantity entering the firstphotodetector 114 of the reflection light detector 164 is higher thanthe light quantity entering the second photodetector 115. The signalsare shown in a and b of FIG. 9. The signals from the first photodetector114 and the second photodetector 115 are amplified by the amplifiers 131and 135, and the difference is taken by the differential amplifier 132.This signal is given by c in FIG. 9. When the output signal of thedifferential amplifier 132 is synchronously detected by a clock 1 fromthe oscillator circuit 140, positive voltage (given by d in FIG. 9) tobias voltage is obtained. When synchronous detection is performed by aclock 2, negative voltage (given by e in FIG. 9) to bias voltage isobtained. Taking the difference between the voltages obtained bysynchronous detection (d-e), the output of the differential amplifier134 is obtained as positive voltage (given by f in FIG. 9) to biasvoltage.

In case of the reflection laser beam not passing through the λ/4birefringence member 123, light quantity entering the secondphotodetector 115 of the reflection light detector 164 is higher thanthe light quantity entering the first photodetector 114. The signals areshown by h and i in FIG. 9. The signals from the first photodetector 114and the second photodetector 115 are amplified by the amplifiers 131 and135, and the difference is taken by the differential amplifier 132. Thissignal is given by j in FIG. 9. When the output signal of thedifferential amplifier 132 is synchronously detected by the clock 1 fromthe oscillator circuit 140, negative voltage (given by k in FIG. 9) tobias voltage is obtained. When synchronous detection is performed by theclock 2, positive voltage (given by 1 in FIG. 9) to bias voltage isobtained. Taking the difference between the voltages obtained bysynchronous detection (k-1), the output of the differential amplifier134 is obtained as negative voltage (given by m in FIG. 9) to biasvoltage.

In case the object reflector 168 shown in FIG. 8 or FIG. 10A is scannedby the polarized laser beam, the output of the differential amplifier134 of the reflection light detection circuit 116 has a waveform shownin FIG. 10B. In case a positive signal is found in the output of thedifferential amplifier 134 and the falling of the negative signal isfound within a given time from the falling of the positive signal, theposition discriminator 117 identifies that it is the object reflector168 and further determines that the position of boundary (where signalvalue is 0) is the center of the object reflector 168. In case theobject reflector 168 is used, if rotating direction of the polarizedlaser beam is reverse, it is needless to say that the sign (+ or -) ofthe output signal of the differential amplifier 134 of the reflectionlight detection circuit 116 is reversed.

The correction of the direction of the main unit 4 after the center ofthe object reflector 168 has been identified is similar to what has beendescribed for the above embodiment, and detailed description is notgiven here.

Description is now given on a third embodiment referring to FIG. 11. Inthe third embodiment, the emitter 162 is changed in such manner that thelaser beam emitted from the laser diode 101 is also emitted in downwarddirection.

The optical axis of the laser diode 101 is directed perpendicularly tothe rotating center of the laser projector 10, and a half prism 125 isarranged at the intersection. Further, a reflection mirror 126 isdisposed at a position on the side of the half prism 125 opposite to thelaser diode 101, and a condenser lens 127 is arranged between the halfprism 125 and the laser diode 101. The laser beam emitted from the laserdiode 101 and reflected by the half prism 125 is directed toward thepentagonal prism 18, and the laser beam, passing through the half prism125, reflected by the reflection mirror 126 and reflected by the halfprism 125, is directed in downward direction. Because the laser beam issent in downward direction, it is possible to easily identify whetherthe main unit 4 is correctly installed at the reference position andthis facilitates the operation to set the main unit 4 at the referenceposition.

FIG. 13 shows an embodiment where the main unit rotator 151 iseliminated and the surveyor corrects the direction of the main unit 4manually according to the display on the display unit 118. The samecomponent as in FIG. 1 is referred by the same symbol, and detaileddescription is not given here.

As shown in FIG. 14, the rotation base 152 is fixed on the lower surfaceof the battery box 45, and the rotating shaft 153 is protruded at aposition lower than the rotation base 152. The rotation frame 154 isfixed on the rotation base 152, and the rotation frame 154 is rotatablymounted on a hollow fixed frame 156 via a bearing 155. The rotatingshaft 153 passes through the rotation frame 154. A fixed collar 145 isengaged with the rotating shaft 153, and a worm wheel 147 is engagedwith the lower end of the rotating shaft 153 with a wave washer 146therebetween. A fine adjustment rod 142 rotatably passing through thefixed frame 156 is provided, and a worm gear 143 engaged with the wormwheel 147 is formed at the forward end of the fine adjustment rod 142.In the fixed collar 145, a fixing screw 148 rotatably passing throughthe fixed frame 156 is screwed, and the forward end of the fixing screw148 can be brought into contact with the rotating shaft 153.

Next, description will be given on adjustment of the direction of themain unit 4.

For rough adjustment, the fixing screw 148 is loosened, and the mainunit 4 is manually rotated in a given direction. Between the worm wheel147 and the rotating shaft 153, friction force caused by the wave washer146 is applied, and when rotating force applied on the main unit 4 isincreased larger than the friction force, it can be rotated manually.For fine adjustment, the fine adjustment rod 142 is rotated, and themain unit 4 can be rotated with fine adjustment via the worm gear 143and the worm wheel 147.

It is possible to accurately direct the main unit 4 toward a givendirection. When the direction of the main unit 4 is determined, thefixing screw 148 is tightened to lock the main unit 4.

In another embodiment, the index of the encoder may be placed at aplurality of positions such as 0°, 90°, 180°, 270°, etc., and theposition of the object reflector can be easily confirmed by comparingthe position of the object reflector with each of these positions. Byproviding the indices at a plurality of positions, the main unit 4 canbe identified promptly. Or, an angle display disk 129 having referenceposition detecting marks at 0°, 90°, 180° and 270° as shown in FIG. 12maybe provided on the display unit 118 so that the direction of the mainunit 4 is displayed by light point on the angle display disk 129 and thesurveyor can visually find the direction of the main unit 4. The halfprism 125 maybe an optical element such as half mirror, beam splitter,etc. to split the laser beam. Further, the laser survey instrument has amechanism tiltable in two directions with respect to the horizontalplane in the above embodiment, while it is needless to say that thepresent invention can be applied to a laser survey instrument, which hasa mechanism tiltable in one direction only.

In the embodiment shown in FIG. 1, the direction of the main unit 4 iscorrected by feedback control to detect rotating angle of the main unit4 with respect to the fixed frame 156 by the encoder 150, and a servomotor or the like is used as the rotating motor 160, while the encoder150 may be eliminated. In this case, a pulse motor is suitable as themotor. Its operation is described below.

By the rotating motor 160, the main unit 4 is rotated in a direction tobe corrected via the rotating gear 157. While rotating the main unit 4,the rotating unit 163 is rotated. The rotating unit 163 is rotated, andthe laser beam is irradiated on the object reflector 168. Then, adeviation when the reflection light from the object reflector 168 isdetected is calculated. When the deviation is turned to 0 by repeatingthe above procedure, it is determined that the direction of the mainunit 4 is aligned with the predetermined direction and that the mainunit has been rotated by an angle of ω toward the direction to becorrected.

In the above embodiment, the object reflector (target) 168 is placed ina direction to be tilted and at a tilting position, and the direction ofthe instrument itself is corrected by turning the main unit 4approximately in that direction. By changing the object reflector 168,it is possible to correct the tilt angle itself and to perform correctsetting.

In the following, description will be given on a fourth embodiment, inwhich tilting direction and tilt angle can be corrected, referring toFIG. 15. FIG. 15 is a block diagram of a control system of theembodiment corresponding to FIG. 2 as described above. The mechanicalportion and the optical system of the instrument are the same as theabove embodiment, and detailed description is not given. Reference ismade now to FIG. 1.

In the following, description will be given only on the features, whichare different from those in the embodiment of FIG. 2.

The output of the position discriminator 117 is inputted to a controller171, which generally controls motor controllers 89 and 90 forcontrolling level adjusting motors 31 and 32, tilt driving circuits 83and 84 for controlling tilting motors 58 and 59, a controller 96 forindicating tilt angle, and a rotation controller 169 for controllingrotation of the rotating unit 163 to rotate the main unit 4.

To the motor controllers 89 and 90, manual controllers 172 and 173 areconnected. By manually operating the manual controllers 172 and 173, thelevel adjusting motors 31 and 32 can be directly controlled. The manualcontrollers 172 and 173 are equipped with push-button switch or jogshuttle to control rotating direction and speed of the motor.

Description is given on operation of this embodiment, referring to FIGS.16A, 16B, 16C and 18.

The instrument is installed at a given position where tilting should beset using a tripod. The main unit 4 is directed approximately in thedirection to be tilted. In this case, a foresight and a backsightbelonging to the main unit 4 may be used. The object reflector 168 isinstalled at a position where tilting should be made (FIG. 16A).

Here, the object reflector 168 used in the present embodiment isdescribed in connection with FIG. 20A. In this object reflector,reflection layers 122 are placed at symmetrical positions, i.e. above,below, left and right with respect to the center of the substrate 121.In FIG. 20A, the reflection layers 122 are formed on peripheral areas ofthe substrate 121 with a rectangular shape. When the laser beam isirradiated in vertical direction to scan the object reflector 168, twopulse-like reflection laser beams are received as shown in FIG. 20B asin the case of scanning in horizontal direction. By calculating theposition of the center of gravity of the light beam received, the centerposition in vertical direction can be identified.

Then, the instrument is operated. After the instrument is installed onthe horizontal reference plane, rotating irradiation of the laser beamis started, and scanning is performed in the tilting direction (FIG.16B). Scanning in the tilting direction and operation of the mechanismhave already been described in the above embodiment, and detaileddescription is not given here.

When the reflection laser beam from the object reflector 168 isdetected, the main unit 4 is rotated, and the tilting direction is set.After the tilting direction has been set, rotation is stopped whileirradiating the laser beam to the object reflector 168. The leveladjusting motors 31 and 32 are operated, and the laser projector 10 istilted. In this case, it will suffice if the laser beam is approximatelyat the center of the target.

Scanning is performed in horizontal tilting direction and the center ofgravity is obtained. At the same time, scanning is performed to obtainthe center of gravity in vertical direction. Reciprocal scanning isperformed to detect the upper and the lower reflection layers, and thecenter of gravity is obtained. If the laser beam is deviated from thecenter of the target, the direction to be tilted is shown by the arrows118d and 118e in the display unit 118. When the tilting in a giventilting direction is set, the controller 171 operates the tilting motors58 and 59. The tilting motors 58 and 59 are operated, and the tiltingplate 62 is tilted until the arbitrary angle setting bubble tube 65 isturned to horizontal direction. By converting the number of pulses ofthe tilting motors 58 and 59 from the preset tilting until the arbitraryangle setting bubble tube 65 is turned to horizontal direction, thesetting tilt angle is obtained (FIG. 16C). The angle is displayed on thedisplay unit (not shown) on the controller 171. In case the presettilting is to be changed, switch or jog shuttle of the manualcontrollers 172 and 173 are used while watching the display unit 118 orthe display unit of the controller 171. The tilting motors 58 and 59 areoperated by the number of pulses corresponding to the tilting to bechanged, and the arbitrary angle setting bubble tubes 65 and 66 aretilted. When the level adjusting motors 31 and 32 are operated so thatthe arbitrary angle setting bubble tubes 65 and 66 are turned inhorizontal direction, tilting is changed. The number of pulses of thetilting motors 58 and 59 are converted to correction angle, and tiltangle is displayed. The level adjusting motors 31 and 32 may be directlyoperated to change the tilting, and the tilting may be converted fromthe number of pulses and displayed.

In case tilt angle is large as shown in FIGS. 17A, 17B and 17C and thelaser irradiating position is apparently deviated from the objectreflector 168 after setting has been made to the horizontal referenceplane, the setting is made for once to the horizontal reference plane.Then, it is switched over to manual control, and the tilting directionand the laser irradiating direction are tilted approximately toward thedirection of the object reflector 168 using the foresight and thebacksight belonging to the main unit. The object reflector in the turneddirection can be confirmed by the reflection of the laser beam. Afterinstalled, it is again switched over to automatic scanning while beingtilted, and similar setting operation is performed after switching.

Next, description will be given on operation in case the objectreflector 168 as shown in FIG. 21A is used.

On the object reflector 168, the portion without the reflection layers122 is arranged diagonally in belt-like form, and the reflection layer122 is divided into two portions: a reflection layer 122a in form of aright-angled triangle, and a reflection layer 122b in form of aninverted right-angled triangle, and these are arranged in such mannerthat the widths of the divided reflection layers 122a and 122b inscanning direction are in inverse proportion to each other as thescanning position is moved.

The signal obtained when the object reflector 168 is used is as shown inFIG. 21B, and what is to be obtained is found where the widths of thesignals of the reflection laser beam from the divided reflection layers122a and 122b concur, i.e. where the angles obtained by the encoder 105concur on the two reflection layers. Thus, the position of tilt anglecan be determined only by scanning in horizontal direction and withoutscanning in vertical direction. There is no need to stop scanning of thelaser beam, and working efficiency is high.

FIG. 22A also shows the case where the reflection layer 122 of theobject reflector 168 is divided into two portions. In this case, each ofthe reflection layers 122a and 122b are designed in a crest-liketriangle with vertexes facing to each other and arranged symmetricallywith respect to the vertical center line. On this object reflector 168,the laser beam is irradiated as in the case of the object reflector 168of FIG. 21A by rotary scanning in horizontal direction. By moving thescanning position continuously in vertical direction, the centerposition in vertical direction can be detected. In case the objectreflector 168 shown in FIG. 22A is used, the obtained signal is as shownin FIG. 22B, and the center is in a direction where the signals of thetwo reflection laser beams increase, and the center is located at themaximum value of the signal. The tilting is determined by the detectionof the center position, and the tilting motors 58 and 59 are operated.The value of the signal is not limited to the maximum value, and thereflection layers may be arranged to cause the minimum value.

In FIG. 23, the reflection layers 122 of the object reflector 168 arearranged in form of narrow belt, two along lateral end and one along thediagonal line to provide an N-shaped reflection layers 122 as a whole.In case this object reflector 168 is used, the signal of the laser beamreflected by scanning of the object reflector 168 by the laser beam isturned to three-pulse signals, and the second signal position is changedaccording to the scanning position. When the second pulse signalposition is at the center of the pulse signals at both ends, it is thecenter of the object reflector 168. Thus, by detecting three-pulsepositions, the center of the object reflector 168 can be detected. Theoperation after the center of the object reflector 168 has been detectedis the same as described above, and detailed description is not givenhere.

FIG. 26 is a diagram of an embodiment corresponding to FIG. 6, and theobject reflector 168 shown in FIG. 27A is used. On a rectangularsubstrate 121, a reflection layer 122 is arranged. On one of the twoportions divided by the diagonal line, λ/4 birefringence member 123 isattached, and the other half is the exposed portion of the reflectionlayer 122. The exposed portion serves as a polarized light maintainingreflecting unit for reflecting the light while maintaining direction ofpolarization of the incident light beam, and the λ/4 birefringencemember 123 serves as a polarized light converted reflecting unit, whichreflects the light while converting direction of polarization from thatof the incident light beam. It is arranged in such manner that the widthof the scanning direction is in inverse proportion to each other as thescanning position is moved between the exposed portion of the reflectionlayer 122 and the λ/4 birefringence member 123.

In the embodiment shown in FIG. 26, circularly polarized laser beam isirradiated from the emitter 162, and there is provided an optical systemfor identifying the reflection laser beam having a different phase inthe reflection light detector 164. As in the embodiment shown in FIG. 6,on the reflection optical axis of the perforated mirror 103, a condenserlens 110, a second λ/4 birefringence member 111, a pinhole 112, apolarized beam splitter 113, and a first photodetector 114 comprising aphotodiode and the like are sequentially arranged in this order as seenfrom the perforated mirror 103, and a second photodetector 115comprising a photodiode and the like is arranged on the reflectionoptical axis of the polarized light beam splitter 113. Outputs from thefirst photodetector 114 and the second photodetector 115 are inputted tothe reflection light detection circuit 116.

The polarized light beam splitter 113 splits the polarized reflectionlaser beam entering the reflection light detector 164 and allows thesplit beams to enter the first photodetector 114 and the secondphotodetector 115. The second λ/4 birefringence member 111 and thepolarized light beam splitter 113 are arranged in such manner that thelaser beam emitted from the emitter 162 and returned to the main unitafter passing through the λ/4 birefringence member twice, i.e. thepolarized reflection laser beam, enters the first photodetector 114, andthe laser beam from the reflection layer 122 having a differentdirection of polarization from that of the above laser beams enters thesecond photodetector 115.

Although not specifically explained, it is equipped with the reflectionlight detection circuit 116 which detects the polarized reflection laserbeam as shown in FIG. 7.

The reflection laser beam reflected by the exposed portion of thereflection layer 122 is deviated by λ/2 in phase from the reflectionlaser beam reflected by the λ/4 birefringence member 123. Accordingly,in the two reflection laser beams converted to linearly polarized lightby the second λ/4 birefringence member 111, the plane of polarization isdeviated by 90°. Therefore, between the reflection laser beams reflectedby the exposed portion of the reflection layer 122 and the reflectionlaser beam reflected by the λ/4 birefringence member 123, the lightquantity entering the first photodetector 114 is different from thelight quantity entering the second photodetector 115 as shown in FIG.27B.

When the laser beam is rotated and irradiated to scan the objectreflector 168 and the scanning position is moved in vertical direction,the intensity of the signal changes in inverse proportion between thereflection laser beam reflected by the exposed portion of the reflectionlayer 122 and the reflection laser beam reflected by the λ/4birefringence member 123. The point where the two signals concur is thecenter of the object reflector 168, and the center of the objectreflector 168 can be detected by the reflection light detection circuit116. The operation after the center of the object reflector 168 has beendetected is the same as described above.

Description is now given on tilting direction and tilt angle settingoperation in case the object reflectors shown in FIGS. 21, 22, 23 and 27are used, referring to FIG. 19. The instrument is set to the horizontalreference plane as in case where the object reflector of FIG. 20 isused, and the laser beam is rotated and irradiated, and scanning isperformed in tilting direction. When the reflection light from theobject reflector 168 is detected, the main unit 4 is rotated, and thetilting direction is set.

The rotating unit 163 is rotated while irradiating the laser beam afterthe tilting direction has been set. The level adjusting motors 31 and 32are operated, and the laser projector 10 is tilted.

As described above, scanning is performed in horizontal direction whilechanging the irradiating position with respect to the object reflector168 in vertical direction. Then, the center position of the objectreflector 168 can be detected, and the tilt angle can be set anddisplayed without stopping the instrument.

Further, description is given on an improved example of the objectreflector 168, referring to FIGS. 24, 25A and 25B.

Normally, when the reflection laser beam is received from the objectreflector, photodetection signal does not start up as clearly soon asthe light is received, but it starts up with a somewhat ambiguous orindefinite inclination as the periphery of the spot light of thereflection laser beam is less luminous than the center of it. Thisambiguousness or indefiniteness can be eliminated when the polarizedlight maintaining reflecting surface and the polarized light convertedreflecting surface are provided and the boundary between the twosurfaces is detected.

Description is given on the object reflector 168, referring to FIGS. 24,25A and 25B. On this object reflector 168, tablet-like reflection layers122a and 122b are arranged on left and right portions of the substrate121 respectively, and the central portion of the substrate 121 isexposed in tablet-like shape. Also, λ/4 birefringence members 123a and123b are attached to overlap on the right half of each of the reflectionlayers 122a and 122b, and two sets of combined reflecting units having acombination of the polarized light maintaining reflecting surface andthe polarized light converted reflecting surface are provided. Thereflection layers 122a and 122b may be arranged in such manner that notonly the central portion of the substrate 121 but also the peripheralportions are exposed. Also, 3 sets or more of the combined reflectingunits may be provided.

In case the scanning with the laser beam is performed on the objectreflector 168 as shown in FIG. 25A, output signal from the differentialamplifier 134 is as shown in FIG. 25B, and two signals can be obtainedwhich have reversed signs (+ and -) definitely divided at thenon-reflecting portion. By detecting the point of reversal of the signsof the signals, i.e. the boundary between the polarized lightmaintaining reflection surface and the polarized light convertedreflecting surface, ambiguousness or indefiniteness of the start-up ofthe signal can be eliminated, and it is possible accurately andcorrectly to identify that it is the light beam reflected from theobject reflector. Further, the time difference t between the two signalshaving reversed signs is specific to the object reflector 168. Thus, bydetecting the time difference t, it is possible to accurately identifythat it is the object reflector 168. Even when there is reflection lightfrom an object such as laminated glass, it can be easily identified fromthe reflection light reflected by floor surface, and erroneous operationdoes not occur.

Because the combined reflecting portion having a polarized lightmaintaining reflecting surface and a polarized light convertedreflecting surface is arranged in belt-like form and these are arrangedon both lateral edges of the substrate 121 or arranged in diagonaldirection as shown in FIG. 23, the target center of the object reflectorcan be accurately detected.

As described above, it is possible according to the present invention toeasily align the laser survey instrument with the reference positionbecause the installing direction of the survey instrument is detected bythe survey instrument itself, because there is no man-made error anddetection is made accurately, and because laser beam is emitted indownward direction. In particular, it is useful when the laser surveyinstrument is to be installed at a position higher than the groundsurface.

What we claim are:
 1. A laser survey instrument, comprising at least amain unit for emitting a laser beam and an object reflector forreflecting the laser beam from the main unit toward the main unit,wherein said object reflector has a reflection surface by which theposition can be discriminated, and said main unit comprises an emitterfor emitting the laser beam, a rotating unit for irradiating the laserbeam to form a laser plane, a tilting mechanism for tilting saidrotating unit at an arbitrary angle at least in one direction and fortilting the laser plane, a reflection light detector for detectingreflection light object reflector, a position discriminator fordetecting the tilting deviation of the irradiated laser beam withrespect to the object reflector based on signals from said reflectionlight detector, and a controller for controlling the tilting mechanismto correct said tilting deviation based on the detection of the positiondiscriminator.
 2. A laser survey instrument according to claim 1,comprising a rotating angle detector interlocked with the rotating unitfor detecting irradiating direction of the laser beam, a rotator forrotating the tilting mechanism, said position discriminator furtherdetecting the deviation of the tilting direction of the main unit andfurther detecting the tilting deviation of the irradiated laser beamwith respect to the object reflector based on signals from said rotatingangle detector, and said controller further controlling the tiltingmechanism to correct the tilting deviation after correcting thedeviation of the tilting direction.
 3. A laser survey instrumentaccording to claim 1 or 2, wherein the reflection light detector detectsthe position of the center of gravity of the reflected photodetectionsignal and to identify the center of the object reflector.
 4. A lasersurvey instrument according to claim 1 or 2, wherein the emittermodulates the laser beam and the reflection light detector is providedwith an electric filter for detecting the modulated laser beam.
 5. Alaser survey instrument according to claim 2, wherein said rotator isarranged to be manually rotatable, and has a limitter which permits themain unit to rotate by a rotating power exceeding a preset power.
 6. Alaser survey instrument according to claim 2, further comprising adisplay unit for displaying a deviation of direction of the main unitwith respect to the object reflector.
 7. A laser survey instrumentaccording to claim 2, wherein the rotating angle detector is an encoderand said encoder has at least one index for detecting the irradiatingdirection of the laser beam.
 8. A laser survey instrument according toclaim 1 or 2, wherein a width of a reflection layer formed on the objectreflector is gradually changed in vertical direction.
 9. A laser surveyinstrument according to claim 1 or 2, wherein a width of a reflectionlayer formed on the object reflector has an extreme value at a givenposition in vertical direction.
 10. A laser survey instrument accordingto claim 1 or 2, wherein the object reflector has reflection layersdivided into two portions, and widths of said two reflection layers arechanged as positions are changed in vertical direction.
 11. A lasersurvey instrument according to claim 1 or 2, wherein the laser beam isincident on the object reflector as circularly polarized light, theobject reflector has a polarized light maintaining reflecting surfacefor reflecting the light while maintaining the circularly polarizedlight of the incident laser beam and a polarized light convertedreflecting surface for reflecting the light in circularly polarizedlight different from the circularly polarized light of the incidentlaser beam, and widths of said two reflecting surfaces are changed asthe positions are changed in a vertical direction.
 12. A laser surveyinstrument according to claim 8, wherein irradiating and scanningposition of the object reflector is moved in a vertical direction, andthe reflection light detector detects the center of a target in thevertical direction based on the change in the width of the laser beamreflected from the object reflector.
 13. A laser survey instrumentaccording to claim 1 or 2, wherein a tilt angle is displayed on adisplay unit based on output from the tilting mechanism corresponding tothe tilting of the tilting mechanism.
 14. A laser survey instrumentaccording to claim 8, wherein a tilt angle is displayed on a displayunit based on output from the tilting mechanism corresponding to thetilting of the tilting mechanism in case the target center of the objectreflector is detected.
 15. A laser survey instrument according to claim1, wherein there is provided manual controlling means for manuallycontrolling the tilt setting of the tilting mechanism.
 16. A lasersurvey instrument according to claim 1 or 2, wherein the laser lightbeam irradiated by the unit is a circularly polarized light beam.
 17. Alaser survey instrument according to claim 10, wherein the objectreflector is divided into two portions by a non-reflection zone.
 18. Alaser survey instrument, comprising an emitter for emitting the laserbeam, a rotating unit for irradiating the laser beam to form a laserplane, a tilting mechanism for tilting said rotating unit at anarbitrary angle at least in one direction and for tilting the laserplane, a reflection light detector for detecting reflection light froman object reflector having a reflection surface by which the positioncan be discriminated, a position discriminator for detecting the tiltingdeviation of the irradiated laser beam with respect to the objectreflector based on signals from said reflection light detector, and acontroller for controlling the tilting mechanism to correct the tiltingdeviation based on the detection of the position discriminator.